There are two tables involved:
1) SY_TabControlSettings - These are settings that relate to the tab control as a whole.
2) SY_TabSettings - These are settings that relate to an invidual tab.
Here are my observations using a tab with no entries in either table:
If you choose "Use Custom Tabs" for a tab strip, you get an entry placed SY_TabControlSettings, but a blank TabOrderXML value. You also get an entry for each tab in the tab control inserted into the SY_TabSettings table.
As soon as you change the tab order, a value for TabOrderXML is placed into SY_TabControlSettings for that tab control. TabOrderXML contains ordering information for ALL tabs that make up that tab control.
Entries in these tables are not deleted at any point, i.e. if you untick "Use Custom Tabs", the entries remain in the tables.
So, I believe the answer to your question is "everything that could potentially be customised is stored."


